JPS6244973B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel fluorination catalyst, and more specifically to a novel fluorination catalyst that reacts chloroaliphatic hydrocarbons and chlorofluoroaliphatic hydrocarbons with hydrogen fluoride to replace chlorine in these compounds with fluorine. This invention relates to novel catalysts for hydrogenation reactions. Various fluorination reaction catalysts have been known so far, among which chromium () compounds, such as chromium chloride (), chromium fluoride (), further chromium fluoride reacted with oxygen, or chromium oxide or Chromium oxyfluoride, which is obtained by reacting hydrogen fluoride with chromium hydroxide, is well known. These catalysts are highly active and effective. However, when used as a catalyst, it is formed into pellets, but the pellets have a weak holding power. In other words, these catalysts deteriorate when used in long-term fluorination reactions, so they are often heated at 400-500°C in an oxygen stream.
It is necessary to reactivate the pellets by heating them to a certain temperature, but each time a part of the pellets is crushed and
Eventually, it becomes powdered and becomes unusable. This is due to the formation of crystalline chromium oxide () and is difficult to avoid. In contrast, it has been proposed to impregnate aluminum fluoride with chromium chloride () or chromium trioxide in the form of granules or pellets, heat-treat the impregnated aluminum fluoride, and treat it with hydrogen fluoride. Although this catalyst has sufficient retention power, its activity, however, cannot be said to be sufficient. An object of the present invention is to provide a catalyst that maintains a strong granular or pellet form that does not break during reactivation treatment and has sufficient activity. This objective can be achieved with a catalyst comprising chromium trioxide supported on aluminum fluoride and treated with chlorofluorohydrocarbons or fluorohydrocarbons at temperatures between 250 and 400°C. Therefore, the catalyst of the present invention has superior activity compared to conventional catalysts using aluminum fluoride as a carrier, does not break during reactivation treatment with oxygen, and is mechanically extremely strong. The aluminum fluoride used as a carrier in the present invention is obtained by fluorinating activated alumina with hydrogen fluoride at 100 to 450°C, and β- or γ-aluminum fluoride is preferable. Therefore, in order to support chromium trioxide on aluminum fluoride, aluminum fluoride may be impregnated with an aqueous solution of chromium trioxide. The amount of chromium trioxide supported on aluminum fluoride is suitably 1 to 10% by weight based on the weight of aluminum fluoride. Generally, the greater the amount of chromium trioxide supported, the higher the activity of the resulting catalyst. When the supported amount is less than 1% by weight, the activity is low and such a substance is not suitable for industrial production of fluorine-substituted products produced by the reaction utilized. No increase was observed. The aluminum fluoride carrying chromium trioxide is then treated with a chlorofluorohydrocarbon or a fluorohydrocarbon at 250-400°C. The chlorofluorohydrocarbon or fluorohydrocarbon used here is preferably a gas at 250 to 400° C. for handling purposes, and preferably has 1 to 4 carbon atoms. Although unsaturated hydrocarbons cannot be used, they are not preferred because they may form polymers on the material to be treated and turn into tar. Carbon number 1
The saturated compounds of ~2 are particularly preferred because they are gaseous at room temperature or become gaseous when slightly heated, making them easy to handle. Examples include dichlorotrifluoroethane and dichlorodifluoromethane. When the treatment temperature is lower than 250°C, the treatment takes too long and is inappropriate, and it is unnecessary to set the treatment temperature higher than 400°C. The treatment time is preferably set until the generation of carbon dioxide stops, but if a certain amount of carbon dioxide is generated, the treatment may be terminated at that point. Depending on the type of chlorofluorohydrocarbon or fluorohydrocarbon, in the case of chlorofluorohydrocarbon 2 to
10 hours is appropriate. The fluorination reaction in which the catalyst of the present invention acts is a fluorination reaction of chlorine in which a chloroalkane or chlorofluoroalkane having 1 to 4 carbon atoms or a chloroalkene or chlorofluoroalkene having 2 to 4 carbon atoms is reacted with hydrogen fluoride. It is. Note that these reactions are carried out under various conditions depending on the ease of substitution of each compound and the number of substituted atoms.
Usually, the reaction temperature is 100 to 500℃, and the reaction pressure is 1 to 10℃.
The atmospheric pressure and space velocity are 100 to 4000 hr ^-1 , and the ratio of hydrogen fluoride to 1 mol of starting material is 0.5 to 20 mol. Next, the present invention will be explained in more detail by showing Examples and Comparative Examples. Example 1 100 g of granular activated alumina (KHA-46 manufactured by Sumitomo Chemical Co., Ltd.) with a particle size of 4 to 6 mm was filled into a 3/4 inch Hastelloy C pipe, heated to 200°C in a nitrogen stream, and then replaced with nitrogen. 200% of hydrogen fluoride
When running at ml/min, the hot spots finished passing through the activated alumina layer after about 6 hours. Next, the temperature was raised to 400°C while passing hydrogen fluoride at the same flow rate.
The hydrogen fluoride treatment was continued for 2 hours, and when the dehydration was almost completed, the hydrogen fluoride was replaced with nitrogen and cooled. According to X-ray diffraction, the product thus obtained was a mixture of β-aluminum fluoride and γ-aluminum fluoride. 30g of granular aluminum fluoride obtained in this way
After placing it in a container and evacuating it, a 20% by weight aqueous solution of chromium trioxide was added to the container. After drying the granular aluminum fluoride that has absorbed an aqueous chromium trioxide solution at 150°C in the air for 10 hours, and heating it to 350°C in a nitrogen stream, it is dried into 1,2-dichloro-1,1,2,2-tetrafluoroethane. Under atmospheric pressure, space velocity
It lasted for 5 hours at 200hr ^-1 . The entire amount of the catalyst thus obtained was packed into a 3/4-inch Hastelloy C reaction tube (length 1000 mm), heated in an electric furnace, and trichlorethylene and hydrogen fluoride were mixed at a reaction temperature of 350°C and a reaction pressure of atmospheric pressure. It passed at a ratio of 3.3 moles of hydrogen fluoride to 1 mole and at a space velocity of 1100 hr ^-1 . The exhaust gas was sequentially passed through a water washing tower, an alkali washing tower and a calcium chloride drying tower, and then collected in a dry ice-acetone cold trap. The gas after passing through the calcium chloride drying tower was analyzed by gas chromatography. Every 30 hours, the reaction was stopped and the catalyst was reactivated by passing air at a space velocity of 200 hr ⁻¹ at 420° C. for 2 hours. The reaction was repeated using this reactivated catalyst under the same conditions as above. Reactivation was performed five times in total, and the reaction was performed each time. The conversion rate and selectivity were as shown in Table 1.

[Table] Comparative example Granular aluminum fluoride 30 prepared in Example 1
A 20% by weight aqueous chromium trioxide solution was absorbed in the same manner as in Example 1 using g as a carrier, and after drying in the same manner, the temperature was raised to 450°C in a nitrogen stream, and at that temperature nitrogen was blown under atmospheric pressure at a space velocity of 200 hr. ^-1 lasted for 5 hours.
This made chromium valent. Using the entire amount of the catalyst thus obtained, trichlorethylene and hydrogen fluoride were reacted in the same manner as in Example 1 to produce 1,1,1-trifluoroethane. 30
The results of continuing the reaction over time are shown in Table 2.

[Table] Example 2 The concentration of chromium trioxide aqueous solution was 30% by weight,
A catalyst was prepared in the same manner as in Example 1 except that the flow time of 1,2-dichloro-1,1,2,2-tetrafluoroethane was changed to 7.5 hours. Using the entire amount of the catalyst thus obtained, trichlorethylene and hydrogen fluoride were reacted in the same manner as in Example 1 to produce 1,1,1-trifluoroethane. The conversion rate of trichlorethylene after 2 hours is 94
The selectivity of 1,1,1-trifluoroethane was 94 mol%.

Claims (1)

[Scope of Claims] 1. A fluorination catalyst characterized in that chromium trioxide supported on aluminum fluoride is treated with a chlorofluorohydrocarbon or a fluorohydrocarbon at a temperature of 250 to 400°C. 2. The catalyst according to claim 1, wherein the aluminum fluoride is β- or γ-aluminum fluoride. 3. The catalyst according to claim 1 or 2, wherein the chlorofluorohydrocarbon or fluorohydrocarbon has 1 to 4 carbon atoms. 4. The catalyst according to claim 3, wherein the chlorofluorohydrocarbon is dichlorotetrafluoroethane. 5. Claims 1 to 5, wherein the amount of chromium trioxide supported is 1 to 10% by weight based on aluminum fluoride.
The catalyst according to any one of Item 4.